You can purchase OMI tokens at:
https://ascendex.com/en/cashtrade-spottrading/usdt/omi
https://www.bitforex.com/en/spot/omi_usdt
https://www.gate.io/trade/OMI_USDT
https://www.okex.com/trade-spot/omi-usdt
https://app.uniswap.org/#/swap?inputCurrency=ETH&outputCurrency=0x04969cd041c0cafb6ac462bd65b536a5bdb3a670